Vapor delivery device, methods of manufacture and methods of use thereof

ABSTRACT

A method comprises transporting a first stream of a carrier gas to a delivery device that contains a liquid precursor compound. The method further comprises transporting a second stream of the carrier gas to a point downstream of the delivery device. The first stream after emanating from the delivery device and the second stream are combined to form a third stream, such that the dew point of the vapor of the liquid precursor compound in the third stream is lower than the temperature of the plumbing that transports the vapor to a CVD reactor or a plurality of CVD reactors. The flow direction of the first stream, the flow direction of the second stream and the flow direction of the third stream are unidirectional and are not opposed to each other.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/050,717 filed Jul. 31, 2018, which is a divisional of U.S. patentapplication Ser. No. 14/990,843 filed Jan. 8, 2016 and which issued asU.S. Pat. No. 10,066,296 on Sep. 4, 2018, which is a divisional of U.S.patent application Ser. No. 13/552,054 filed Jul. 18, 2012 and whichissued as U.S. Pat. No. 9,243,325 on Jan. 26, 2016, the content of whichare incorporated by reference herein in their entireties.

BACKGROUND

This disclosure relates to a vapor delivery device, methods ofmanufacture and methods of use thereof. In particular, this disclosurerelates to a high output, high capacity delivery device for deliveringliquid precursor compounds in the vapor phase to reactors.

Semiconductors comprising Group III-V compounds are used in theproduction of many electronic and optoelectronic devices such as lasers,light emitting diodes (LEDS), photodetectors, and the like. Thesematerials are used for manufacturing different monocrystalline layerswith varying compositions and with thicknesses ranging from fractions ofa micrometer to a few micrometers. Chemical vapor deposition (CVD)methods using organometallic compounds are generally employed for thedeposition of metal thin-films or semiconductor thin-films, such asfilms of Group III-V compounds. Such organometallic compounds may beeither liquid or solid.

In CVD methods, a reactive gas stream is generally delivered to areactor to deposit the desired film for electronic and optoelectronicdevices. The reactive gas stream is composed of a carrier gas, such ashydrogen, entrained with vapors of a precursor compound. When theprecursor compound is a liquid (hereinafter liquid precursor compound),a reactive gas stream is generally obtained by passing (i.e., bubbling)a carrier gas through the liquid precursor compound in a delivery device(i.e., a bubbler). The delivery device comprises a bath surrounding acontainer that holds the liquid precursor compound.

Liquid precursor compounds have a specific enthalpy of vaporization of2.0 to 10.0 watt-minute per gram. When there is no carrier gas flowthrough the delivery device the temperature difference between the bathand the liquid precursor compound is zero and no energy is expended inthe delivery device. On the other hand, when it is desired to deliverthe liquid precursor compound to the reactor at a particulartemperature, the carrier gas is permitted to flow through the liquidprecursor compound as a result of which the liquid precursor compoundcools down. This cooling is undesirable because temperature variationsin the liquid precursor compound lead to variable amounts of the liquidprecursor compound being delivered to the reactor. The bath, in order tocompensate for the temperature variations, now transfers energy to thedelivery device in the form of heat in order to attempt to maintain theliquid precursor compound at a constant temperature. The temperaturedifference between the bath and the liquid precursor compound istherefore no longer zero. Since heat is supplied from the bath to theliquid precursor compound, the temperature of the liquid precursorcompound is now not accurately known (i.e., there are temperaturevariations in the liquid precursor compound).

Early liquid precursor compound delivery devices were long, narrowcylinders, i.e. aspect ratio of greater than 2, which were capable ofholding a volume equivalent to 200 grams of a particular liquidprecursor compound. The delivery device therefore had a large surfacearea to liquid precursor compound mass ratio and could easily be fullyimmersed in commercially available constant-temperature baths. Thecarrier gas flows were small and thus temperature differences betweenthe bath and the liquid precursor compound were negligible. The liquidprecursor compound flux in moles per minute was known within 1 weightpercent (wt %) with little change throughout the use of the bubbler.

Current liquid precursor compound delivery devices are larger than theearly liquid precursor compound delivery devices and uselower-aspect-ratio cylinders (that have height-to-diameter aspect ratiosof less than 2) as compared with the earlier devices. Current deliverydevices contain more than 2 kilograms of liquid precursor compound, andmay contain up to 10 kilograms of liquid precursor compound. These largecylinders do not normally fit into commercially availableconstant-temperature baths. Portions of the cylinder top often areexposed to the ambient air and thus become an unintentional source ofheat or cooling to the liquid precursor compound depending upon ambientconditions.

In addition, carrier gas flows of around 1 standard liter per minute andvaporization rates of 1 gram per minute of liquid precursor compound areused in these larger current liquid precursor compound delivery devices,thus using 5 watts of energy for the vaporization. As a result, theliquid precursor compound temperature easily deviates more than 2° C.from the bath temperature, which can result in a deviation in the liquidprecursor compound flux of up to 10 wt %.

Another concern with the larger current liquid precursor compounddelivery devices is the time it takes to reach a steady state ofprecursor compound flux. The chemical process in the reactor cannotproceed until the flux of liquid precursor compound vapors from thedelivery device is stabilized. The time to stabilize the liquidprecursor compound flux depends mainly on heat transfer area and themass of the liquid precursor compound in the delivery device. Both ofthese parameters are only approximately known. Upon starting the carriergas flow, the liquid precursor compound uses its internal heat forevaporation, thus resulting in a cooling down of the liquid precursorcompound. A relatively large liquid precursor compound mass results in arelatively longer time period to reach a steady state temperature,whereas a relatively smaller liquid precursor mass results in arelatively shorter time period to reach a steady state temperature. Thetime it takes to reach a steady state temperature depends on the heattransfer area and on the remaining mass.

There therefore remains a need for improved delivery devices and methodsfor delivering vapors of a liquid precursor compound from a largedelivery device, where at least 1 watts of energy is utilized for thevaporization. It is also desirable to have a delivery device that candeliver a uniform and high flux of the precursor vapor throughout theprocess up to depletion of the liquid precursor compound from thedelivery device, while using carrier gas flows that are greater than 1standard liter per minute.

A delivery system for a liquid precursor compound comprises a deliverydevice having an inlet port and an outlet port; a first proportionalvalve; wherein the delivery device is in operative communication with afirst proportional valve; wherein the first proportional valve isoperative to control the flow of the carrier gas based on an appliedvoltage; a physical-chemical sensor; the physical-chemical sensor beingdisposed downstream of the delivery device and being operative toanalyze chemical contents of a fluid stream emanating from the deliverydevice; the physical-chemical sensor being in communication with thefirst proportional valve; and a first pressure/flow controller being inoperative communication with the physical-chemical sensor and with thefirst proportional valve; wherein the delivery system is operative todeliver a substantially constant number of moles per unit of time of aliquid precursor compound vapor to each of a plurality of reactors thatare in communication with the delivery system; where the liquidprecursor compound is in a liquid state in the delivery device.

A method comprises transporting a first stream of a carrier gas to adelivery device; the delivery device containing a liquid precursorcompound; the first stream of carrier gas being at a temperature greaterthan or equal to 20° C.; transporting a second stream of the carrier gasto a point downstream of the delivery device; wherein a flow directionof the first stream and a flow direction of the second stream are notopposed to each other; and combining the first stream after it emanatesfrom the delivery device and the second stream to form a third stream;where a dew point of a vapor of the precursor compound in the thirdstream is lower than an ambient temperature.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic depiction of an exemplary delivery system where adelivery device is in fluid communication with one or more mass flowcontrollers which are each in fluid communication with a reactor vesseland where vapors from the delivery device are disposed on selectedsurfaces in the reactor;

FIG. 2 is a schematic depiction of an exemplary delivery system where asingle pressure/flow controller controls the flow rate through thedelivery device;

FIG. 3 is another schematic depiction of an exemplary delivery systemwhere a single pressure/flow controller controls the mass flow ratethrough the delivery device;

FIG. 4 is a schematic depiction of an exemplary mixing chamber;

FIG. 5 is a schematic depiction of another exemplary mixing chamber;

FIG. 6 is a schematic depiction of a comparative delivery device thatwas used in the example and was compared with the disclosed deliverydevices;

FIG. 7A is a graph showing performance of the comparative deliverydevice when filled to 40% of its capacity;

FIG. 7B is a graph showing performance of the comparative deliverydevice when filled to 20% of its capacity; and

FIG. 8 is a graph that depicts performance data for the conventionaldelivery device as well as for the disclosed delivery device.

DETAILED DESCRIPTION

The invention now will be described more fully hereinafter withreference to the accompanying drawings, in which various embodiments areshown. Like reference numerals refer to like elements throughout.

It will be understood that when an element is referred to as being “on”another element, it can be directly on the other element or interveningelements may be present therebetween. In contrast, when an element isreferred to as being “directly on” another element, there are nointervening elements present. As used herein, the term “and/or” includesany and all combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, third,etc. may be used herein to describe various elements, components,regions, layers and/or sections, these elements, components, regions,layers and/or sections should not be limited by these terms. These termsare only used to distinguish one element, component, region, layer orsection from another element, component, region, layer or section. Thus,a first element, component, region, layer or section discussed belowcould be termed a second element, component, region, layer or sectionwithout departing from the teachings of the present invention.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. It willbe further understood that the terms “comprises” and/or “comprising,” or“includes” and/or “including” when used in this specification, specifythe presence of stated features, regions, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, regions, integers, steps,operations, elements, components, and/or groups thereof. The transitionterm “comprising” encompasses the transition terms “consisting of and“consisting essentially of.” The term and/or is used herein to mean both“and” as well as “or”. For example, “A and/or B” is construed to mean A,B or A and B.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother element as illustrated in the Figures. It will be understoodthat relative terms are intended to encompass different orientations ofthe device in addition to the orientation depicted in the Figures. Forexample, if the device in one of the figures is turned over, elementsdescribed as being on the “lower” side of other elements would then beoriented on “upper” sides of the other elements. The exemplary term“lower,” can therefore, encompasses both an orientation of “lower” and“upper,” depending on the particular orientation of the figure.Similarly, if the device in one of the figures is turned over, elementsdescribed as “below” or “beneath” other elements would then be oriented“above” the other elements. The exemplary terms “below” or “beneath”can, therefore, encompass both an orientation of above and below.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

Various numerical ranges are disclosed herein. These ranges areinclusive of the endpoints as well as numerical values between theseendpoints. The numbers in these ranges are interchangeable.

Disclosed herein is a delivery system for a liquid precursor thatcomprises a delivery device in fluid communication with a reactor(comprising a mass flow controller and a reactor vessel) via aconcentration sensor and a pressure sensor. The concentration sensor andthe pressure sensor are in electrical communication with a first and asecond pressure/flow controller respectively that control the flow ofcarrier gas through the delivery system. The delivery system uses acarrier gas stream that is split into two carrier gas streams, a firststream that flows into the delivery device and contacts a liquidprecursor compound and a second stream that bypasses the deliverydevice. A liquid precursor is an element or compound that that is in aliquid state from −10° C. to 200° C. at atmospheric pressure.

The splitting of the carrier gas into two streams eliminates the need tomaintain tight control of the temperature of the precursor, such asmaintaining it within a fraction of a degree Celsius. Maintaining such atight control of the temperature at evaporative loads exceeding 1.0 Wattis both difficult and expensive. The flow path of the entire firststream may be heated to an elevated temperature, if desired to counterany heat loss and maintain the temperature closer to the original(expected) value.

The lower flow rate in the first stream when used in conjunction withthe elevated temperature permits the entrainment of a higher volume ofthe precursor vapor. The amount of the precursor vapor transmitted perunit of time across a plane perpendicular to the direction of flow istermed the flux and is measured in moles per minute or in anotherconvenient unit. The process performed in the reactor depends on theprecursor flux. If the precursor flux cannot be precisely maintained,the process results are unpredictable. The precursor vapor flux ishigher in the first stream and zero in the second gas stream in contrastto a comparative system where there is no stream that bypasses theliquid precursor compound.

The delivery system functions to deliver a uniform and constantconcentration of the precursor vapors to the plurality of reactors. Inconjunction with mass flow controllers that are disposed upstream of thereactor, the number of moles of precursor vapor per unit time (i.e., theflux) delivered to the reactor are also kept constant.

The first stream with a high concentration of entrained vapors and thesecond stream that comprises only the carrier gas contact each otherdownstream of the delivery device to form a third stream. The secondstream and the first stream combine to form the third stream. Thecombination of the first stream (entrained with vapor) and the secondstream (devoid of vapor) to form the third stream results in thedelivery of a more precise concentration of the precursor vapor to thereactor especially when compared with a comparative device that does notuse a bypass.

The dew point of the third stream can be adjusted to be below thetemperature of the tubing and hardware that connects the delivery systemand the reactor. In this way, condensation of the liquid precursorinside the connecting tubing is avoided. It is possible to use a varietyof different liquid precursors having different dew points and avoidcondensation of any of these precursors by heating any connecting lines.

The present delivery system is advantageous in that it delivers auniform and precise concentration of precursor vapor to the reactor upto the depletion of the liquid precursor compound from the deliverydevice. It permits precursor fluxes that are greater than or equal to0.5 grams per minute, preferably greater than or equal to 2.0 grams perminute, and more preferably greater than or equal to 10.0 grams perminute to a reactor or a plurality of reactors at a pressure of greaterthan or equal to 120 kilopascals (kPa) (900 torr), preferably greaterthan or equal to 160 kPa (1200 torr), and more specifically greater thanor equal to 200 kPa (1500 torr).

The delivery system is also advantageous because it can provide theprecursor vapors to be delivered to a plurality of reactorssimultaneously. The delivery system balances competing demands from aplurality of reactors and can supply a stream having a uniformconcentration of precursor vapors to each reactor irrespective of thevolumetric demand from individual reactors. The present delivery systemcan deliver a substantially constant concentration of the precursorvapors to each of the reactors.

The concentration of the precursor vapor in the present delivery systemfluctuates in an amount of less than or equal to 1 weight percent (wt %)from a selected value, preferably in an amount of less than or equal to0.5 wt % from a selected value, and more preferably in an amount of lessthan or equal to 0.2 wt % from a selected value. In conventionaldelivery systems, the concentration of precursor vapor fluctuates bymore than 10 wt %.

The delivery system is unique in that it does not utilize any opposingflows without the presence of an optional mixing chamber. In otherwords, the delivery system does not use flows that contact each otherfrom opposing directions. The system may employ an opposing flow onlywhen an optional mixing chamber is used.

As noted above, the delivery system uses a mixing chamber. In oneembodiment, the mixing chamber can be used when the delivery system doesnot use opposing flows. Interactions between the carrier gas and theprecursor vapor in the mixing chamber facilitate better mixing thusensuring a uniform delivery of the precursor vapor to the reactors. Inanother embodiment, the mixing chamber is used only when the deliverysystem employs opposing flows.

With reference now to the FIG. 1, a delivery system 100 comprises adelivery device 102 in communication with a mass flow controller 208 anda reactor 200 via a physical-chemical sensor 104 and a pressure sensor106 respectively. The physical-chemical sensor 104 and the pressuresensor 106 are in operative communication with a first pressure/flowcontroller 108 and a second pressure/flow controller 110, respectively.The first pressure/flow controller 108 is in operative communicationwith a first proportional valve 112, while the second pressure/flowcontroller 110 is in operative communication with a second proportionalvalve 114 respectively. In an exemplary embodiment, the firstpressure/flow controller 108 is in electrical communication with a firstproportional valve 112, while the second pressure/flow controller 110 isin electrical communication with a second proportional valve 114respectively.

The delivery device 102 is not disposed in a water bath that may be usedto vary or stabilize the temperature of the delivery device. It isdevoid of any external sources of heating or cooling other than to beinfluenced by its ambient surroundings. The delivery device 102 is 0.5liters to 100.0 liters in size and is disposed upon a scale 105. Thescale 105 is used to determine the amount of liquid precursor compoundcontained in the delivery device 102. It will be appreciated by thoseskilled in the art that delivery device 102 may be many times larger,such as up to 1,000 liters, but the transport and handling of such alarge delivery device would be complicated.

The proportional valves 112 and 114 operate to control the flow of thecarrier gases through the delivery system 100 when they are disposedupstream of the delivery device 102. In another embodiment, aproportional valve 112 a can also be disposed downstream of the deliverydevice if desired and operates to control the flow of the carrier gasand the precursor vapor. Shutoff valves 116, 118, 120 and 122 are usedto isolate the different components of the delivery device. In oneembodiment, the shutoff valves 116 and 118 are open in normal operation.

When the voltage across the proportional valves 112 and 114 isincreased, the valve opening is increased thereby increasing the flow ofthe carrier gas through the valve. On the other hand, when the voltageacross the proportional valves is decreased, the valve opening isdecreased thereby decreasing the flow of the carrier gas through thevalve.

In one embodiment, the physical-chemical sensor 104 along with the firstpressure/flow controller 108, the first proportional valve 112, and thedelivery device 102 form a first closed loop that encompasses the firststream 202 of carrier gas. The first stream 202 of carrier gas isdirected to a dip tube 103 via an inlet port on the delivery device 102.The first stream is also referred to as the “source flow” stream sinceit contacts the liquid precursor compound in the delivery device 102 andentrains precursor vapor. Since one of the functions of the first streamis to entrain precursor vapor, it is generally maintained at an elevatedtemperature.

The first stream is generally maintained at an ambient temperature of 0°C. to 80° C., preferably 10° C. to 50° C., and more preferably 15° C. to35° C. The first stream 202 entrains vapors of the precursor compound.An outlet port located atop the delivery device 102 facilitates thedischarge of a stream 203 of the carrier gas with entrained vapors ofthe liquid precursor compound. Stream 203 emanates the delivery device102 and contacts the second stream 204 of carrier gas in a mixingchamber 107.

In another embodiment, the pressure sensor 106 along with the secondpressure/flow controller 110, the second proportional valve 114, and themixing chamber 107 form a second closed loop that encompasses a secondstream 204 of carrier gas. The second stream 204 of carrier gas isdirected to the mixing chamber 107 where it contacts the stream 203emanating from the outlet port of the delivery device 102. The secondstream is also referred to as the “bypass flow” stream since it bypassesthe liquid precursor compound in the delivery device 102.

The first stream 202 after exiting the delivery device 102 as stream 203combines with the second stream 204 in the mixing chamber 107 to form athird stream 206 that enters the reactor 200 via the mass flowcontroller 208. The first stream 202, now stream 203, combines with thesecond stream 204 downstream of the outlet valve 122 to form the thirdstream 206, which is directed to the reactor 200. The third stream 206contains the desired concentration of the precursor vapor in the carriergas. As noted above, the stream 203 and the second stream 204 do notoppose each other. In one embodiment, the stream 203 and the secondstream 204 flow in the same direction. In another embodiment, the stream203 and the second stream 204 meet each other at an angle of 1 to 90degrees to form the third stream 206 that enters the reactor 200.

In one embodiment, an optional mixing chamber 107 may be used to combinethe flows from the first stream 202, now stream 203 (which contains thecarrier gas and the precursor vapor from the delivery device 102) andthe second stream 204. In the mixing chamber 107, the flows from thestream 203 and the second stream 204 may be introduced in opposingdirections. In another embodiment, the mixing chamber 107 may be used tocombine the flow from the stream 203 and the second stream 204 whenthese respective streams are not flowing in opposing directions. Both ofthese embodiments will be discussed in greater detail later.

By combining the stream 203 with the second stream 204 to form the thirdstream 206, the concentration of the precursor vapor in the carrier gasis reduced resulting in a lower dew point of the precursor vapor. As aresult, precursor vapor condensation does not occur when the vaporentrained carrier gas encounters a reduced temperature. This permits aconstant ratio of precursor vapor to the carrier gas to be supplied to areactor or a plurality of reactors. In another embodiment, by reducingthe dew point of the precursor vapor in the third stream to below theambient temperature, precursor vapor condensation does not occur and aconstant ratio of precursor vapor to the carrier gas may be supplied toa reactor.

The first and the second closed loops interact collaboratively with oneanother to control the delivery pressure and the precursor vaporconcentration to one or a plurality of reactors 200. The flow rate ofprecursor into each reactor is controlled by the mass flow controller208 associated with each reactor. The first and the second closed loopsalso interact collaboratively with one another to maintain the dew pointof the precursor vapor precisely adjusted below the ambient temperature.This prevents condensation of the precursor vapors and permits thetransportation of a larger amount of precursor vapor at a higherprecision to the reactor than other comparative commercially availablesystems. While the respective loops have been shown to be closed loopsin the FIG. 1, it is envisioned that some of these loops can also beopen loops if desired.

With reference again to FIG. 1, the delivery device 102 has an inletvalve 120 that can be used to start or stop the flow of the carrier gasinto the delivery device 102. The delivery device 102 also has an outletvalve 122 that can start and stop the flow of the carrier gas withentrained precursor vapor from the delivery device 102 to the reactor200. As may be seen in the FIG. 1, the delivery device 102 is in fluidcommunication with the reactor 200, such that precursor vapor from thedelivery device 102 is disposed on selected surfaces in the reactor 200.A mass flow controller 208 admits the desired flow of the mixture to thereactor 200.

The mass flow controller 208 may comprise a single mass flow controlleror a plurality of mass flow controllers, while the reactor 200 maycomprise a single reactor or a plurality of reactors (not shown). In anexemplary embodiment, the mass flow controller 208 and the reactor 200comprises a plurality of mass flow controllers and reactors.

The delivery device 102 contains a dip tube 103 through which thecarrier gas enters and an exit port 109 through which the carrier gasentrained with precursor vapor is discharged to the reactor 200. Theinlet port of the delivery device 102 is in fluid communication with theinlet valve 120 while the exit port of the delivery device 102 is influid communication with the outlet valve 122. In one embodiment, pipesor tubes that are used to transport the carrier gas to the deliverydevice are all maintained at a temperature of 20° C. to 80° C.

The delivery device 102 and the inlet and outlet ports may bemanufactured from a material that is not deteriorated by the carrier gasor the liquid precursor compound and that in turn does not change thecomposition of the carrier gas or the liquid precursor compound. It isalso desirable for the material to withstand the temperatures andpressures of operation. The enclosure may be manufactured from asuitable material, such as, for example, glass, polytetrafluoroethyleneand/or a metal. In one embodiment, the enclosure is constructed of ametal. Exemplary metals include nickel alloys and stainless steels.Suitable stainless steels include SS304, 55304L, SS316, SS316L, SS321,SS347 and SS430. Exemplary nickel alloys include INCONEL, MONEL, andHASTELLOY.

The delivery device 102 generally contains an opening (not shown)through which the liquid precursor compound is introduced. The liquidprecursor compound may be added to the delivery device by any suitablemeans.

The liquid precursor compound is the source of the precursor vapor. Anyliquid precursor compound suitable for use in vapor delivery systems maybe used in the delivery device including solutions and suspensions ofnormally solid compounds. Suitable precursor compounds include indiumcompounds, zinc compounds, magnesium compounds, aluminum compounds,gallium compounds, and combinations comprising at least one of theforegoing compounds or liquid solutions and suspensions of suchcompounds. Preferably, the liquid precursor compounds are chosen fromaluminum compounds, gallium compounds, and combinations comprising atleast one of the foregoing compounds. Mixtures of liquid precursorcompounds may be used in the present delivery devices.

Preferred liquid precursor compounds include boron tribromide,phosphorous oxychloride, phosphorous tribromide, silicon tetrachloride,silicon tetrabromide, tetraethyl orthosilicate, arsenic trichloride,arsenic tribromide, antimony pentachloride, trimethylgallium (TMGa),triethylgallium (TEGa), trimethylaluminum (TMA1), ethyldimethylindium,tertiary-butylarsine, tertiary-butylphosphine, germanium tetrachloride(GeCl₄, stannic chloride (SnCl₄, trimethylarsenic (CH₃)₃As,trimethylgallium (CH₃)₃Ga, triethylgallium (C₂H₅)₃Ga, isobutylgermane(C₄H₉)GeH₃, diethyltelluride (C₂H₅)₂Te, diisopropyltelluride (C₃H₇)₂Te,dimethylzinc (CH₃)₂Zn, diethylzinc (C₂H₅)₂Zn, trimethylantimony(CH₃)₃Sb, triethylantimony (C₂H₅)₃Sb, boron trichloride (BCl₃), chlorinetrifluoride (C₁F₃), trisilane (Si₃H₈), or the like, or a combinationcomprising at least one of the foregoing precursors.

More preferred liquid precursor compounds are trimethylgallium,riethylgallium, trimethylaluminum, tertiary butylphosphine, tertiarybutylarsine, tetraethyl orthosilicate, silicon tetrachloride, germaniumtetrachloride, isobutyl germane, trimethyl antimony, dimethyl zinc,diethyl zinc, or the like, or a combination comprising at least one ofthe foregoing liquid precursor compounds.

A suitable carrier gas may be used with the delivery device 102 as longas it does not react with the liquid precursor compound. The particularchoice of carrier gas depends upon a variety of factors such as theprecursor compound used and the particular chemical vapor depositionsystem employed. Suitable carrier gases include inert gases. Exemplarygases are hydrogen, nitrogen, argon, helium, and the like.

The physical-chemical sensor 104 is a concentration sensor and measuresthe concentration of the precursor vapor in the carrier gas. Thephysical-chemical sensor 104 controls the mass transfer rate of theprecursor vapor into the reactor by continually monitoring gasconcentration and controlling the first stream 202 through the deliverydevice 102 to account for concentration changes and/or drift.

In one embodiment, the physical-chemical sensor 104 is an in-lineacoustic binary gas concentration sensor used for sensing the ratio ofthe precursor vapor to the carrier gas. The physical-chemical sensorgenerates an acoustic signal that travels through the gas mixture (i.e.,the mixture of the vapor of the precursor compound and the carrier gas),using a digital signal processing technique to precisely measure thetime of travel of the acoustic signal. The time of travel is then usedto calculate the concentration of the precursor vapor in the carriergases based upon their physical properties. This concentrationmeasurement provides data that allows for control of the mass transferrate of the precursor vapor while compensating for any variations in theconcentration of the precursor vapor with respect to the carrier gas.This control in the mass transfer rate is brought about by the firstproportional valve 112. Other sensors include micro-electronicmechanical circuits (MEMCs) that also measure the composition of abinary gas by measuring the density.

For example, when the output from the physical-chemical sensor 104 iszero volts it indicates that the concentration of the precursor vapor inthe carrier gas is 0 wt % (weight percent). When the output from thephysical-chemical sensor 104 is 5 volts, the concentration of theprecursor vapor in the carrier gas is 1 wt %. In an exemplaryembodiment, the physical-chemical sensor 104 is a PIEZOCON®,commercially available from Veeco Corporation.

In an exemplary embodiment, when the liquid precursor compound istrimethylgallium, the physical-chemical sensor 104 is used to controlthe flow through the delivery device 102 to provide the delivery system100 with a 15° C. dew point for the trimethylgallium vapor. Thetransport plumbing (i.e., lines that transport the carrier gas and theprecursor vapor) between the delivery device 102 and the mass flowcontroller 208 feeding the reactor 200 are generally maintained at roomtemperature of 20° C. in order to avoid the cost of maintaining thetransport plumbing at temperatures greater than 20° C. In order to keepthe trimethylgallium vapors from condensing in the transport plumbing adew point of 15° C. is selected for the trimethylgallium. This 5° C.difference permits a continuous steady flow of the precursor vapor tothe reactor.

The pressure sensor 106 measures the pressure across the delivery device102. The pressure sensor 106 may be a pressure gauge, a manometer, orthe like. The pressure sensor 106, in combination with the secondcontroller 110, and the second proportional valve 114, provides amechanism to control the pressure of the precursor vapor and the carriergas.

The optional mixing chamber 107 is detailed in the FIGS. 4 and 5. FIG. 4shows the mixing chamber 107 when it contains opposing flows, while FIG.5 shows the mixing chambers 107 when it does not contain an opposingflow.

FIG. 4 depicts the mixing chamber 107 having opposing flows for thestream 203 and the second stream 204. The mixing chamber 107 comprises achamber 300 that is manufactured from a nickel alloy or a stainlesssteel. The chamber 300 may have any shape but is preferably a cylinderwith diameter and height being equal or nearly equal. In one embodiment,it is desirable to have a diameter of the mixing chamber be greater thanor equal to 1 inch (2.5 cm), preferably greater than or equal to 2inches (5 cm) and more preferably greater than or equal to 3 inches (7.5cm). In another embodiment, the height of the cylinder is greater thanor equal to 2 inches (5 cm), preferably greater than or equal to 3inches (7.5 cm) and more preferably greater than or equal to 4 inches(10 cm).

The stream 203 enters the chamber 300 via a conduit 302 while the secondstream 204 enters the chamber 300 via a conduit 304. The third stream206 leaves the chamber 300 via a conduit 306. The position of the mixingchamber 107, when it is used in the delivery system, allows it to be apart of the first closed loop and the second closed loop.

The respective conduits preferably have a circular cross-section with anouter diameter that is greater than or equal to 3 millimeters (mm)(0.125 inches), preferably greater than or equal to 6 mm (0.25 inches)and more preferably greater than or equal to 12 mm (0.5 inches). As maybe seen in the FIG. 4, the outlets of the conduit 302 and 304 areopposed to each other. The outlets of conduits are designed to beopposed to each other and to be less than 12 mm apart from each other sothat the stream 203 and the second stream 204 can be intimately mixedwith each other prior to exiting the chamber via the conduit 306 as thethird stream 206. The conduit 306 is provided with a device 308 forconnecting the chamber 300 to a conduit that is in communication with aninlet (not shown) to the reactor 200.

The conduit 302 is fitted with a baffle 310 that is parallel a side ofthe chamber 300 that communicates with the conduit 304. The baffle 310forces the first stream 202 and the second stream into an intimatemixture with each other in the space 312 between the baffle 310 and theside of the chamber 300.

FIG. 5 depicts the mixing chamber 107 having flows for the stream 203and the second stream 204 that are not opposed to each other. In thisdepiction, the stream 203 enters the chamber 300 via the conduit 302,while the second stream 204 enters the chamber 300 via the conduit 304.The meeting of the two streams in the chamber 300 brings about mixingbetween the two streams 203 and 204, which then depart the chamber 300as the third stream 206 via the conduit 306. In the embodiments depictedin the FIGS. 4 and 5, the conduits 302, 304 and 306 may contain nozzles,porous filters, or other devices that are used to enhance mixing of thestream 203 with the second stream 204. The mixing chamber may alsocontain packing materials such as beads, rods, tubes, horseshoes, rings,saddles, discs, saucers, or other suitable forms such as aciform,cruciform, and helicoids (coils and spirals). The packing material maybe composed of ceramic materials such as alumina, silica, siliconcarbide, silicon nitride, borosilicates, alumina silicates, andcombinations comprising at least one of the foregoing, and/or metalssuch as stainless steel or nickel alloys. Combinations of differentpacking materials listed above may be used if desired. The mixingchamber 107 may be used in any of the embodiments depicted in thefollowing FIGS. 1-3 at the point where the stream 203 contacts thesecond stream 204.

With reference once again to the FIG. 1, the first controller 108 andthe second controller 110 are self-containedproportional-integral-derivative (PID) control modules that are designedto provide optimized control of the total pressure or flow of thecarrier gas through the delivery system 100. The input for the firstproportional valve 112 is obtained from the pressure sensor 106. Theinput for the second proportional valve 114 is obtained from thephysical-chemical sensor 104. Each pressure/flow control systemcomprises three basic parts, notably a process sensor, aproportional-integral-derivative controller and a control element.Controllers 108 and 110 may also be realized as software in ProgrammableLogic Controllers (PLC, such as the Omron CJ1W controller) incombination with appropriate driving hardware for the valves 112 and114.

In the operation of the first proportional valve 112, thephysical-chemical sensor 104 measures the process pressure or carriergas flow rate. The proportional-integral-derivative controller comparesthe measured concentration of the precursor to the desired set point andadjusts the proportional valve 112 as necessary to achieve the desiredprecursor vapor concentration in the third stream 206.

In the operation of the second proportional valve 114, the pressuresensor 106 controls the bypass flow to maintain the programmed pressure.The precursor vapor demands of the reactor 200 are made by the mass flowcontroller 208. In response, the pressure sensor 106 in conjunction withthe flow controller 110 and the second proportional valve 114 adjuststhe flow of the carrier gas in the second stream 204 to provide thedesired pressure in the third stream 206.

In one embodiment, a plurality of pressure/flow controllers can beslaved to a master pressure/flow controller, which adjusts the totalflow of the carrier gases to achieve the desired pressure, while thephysical-chemical sensor 104 and the associated controller 108 maintainsthe desired gas ratio/mixture. For example, the first proportional valve112 and the second proportional valve 114 from the FIG. 1 can be slavedto a main pressure controller (not shown) to divide the total flow ofthe carrier gases to the stream 203 and the second stream 204. Therewould be no active control of the concentration in this embodiment.

The shutoff valves 116 and 118 and the inlet and outlet valves 120, 122may be gate valves, ball valves, butterfly valves, needle valves, or thelike. They may also be controlled by a PLC and support the maintenanceof a precise precursor concentration when the demand from the reactor200 is zero.

In one embodiment, in one manner of utilizing the delivery system 100 ofthe FIG. 1, the reactor 200 draws vapor from the delivery device 102.The carrier gas can be delivered by either the first proportional valve112 or the second proportional valve 114 or both depending upon theinformation provided by the physical-chemical sensor 104 and thepressure sensor 106.

In one embodiment, the carrier gas is optionally heated to a temperaturenot greater than the boiling point of the liquid precursor compound asit travels through the fluid lines (e.g., pipes or tubes) that includethe first stream 202 and the second stream 204. The carrier gas in thefirst stream 202 travels through the delivery device 102 and entrainsthe vapors of the precursor compound. The carrier gas with the vaporentrained therein (stream 203) then meets with the carrier gas in thesecond stream 204. By adjusting the mass flow of the carrier gas in thefirst stream 202 and the second stream 204, the concentration of theprecursor vapor can be maintained at a desired amount.

The “desired amount” is determined by settings of the physical-chemicalsensor 104 and the pressure sensor 106 and the respective pressure/flowcontrollers 108 and 110. The concentration of the precursor vapor in thethird stream 206 is measured by the physical-chemical sensor 104. Thepressure and/or the flow rate of the carrier gas (with precursor vaporentrained therein) are measured by the pressure sensor 106.

When the concentration of the precursor vapor relative to the carriergas deviates from a desired amount or a desired range, thephysical-chemical sensor 104 communicates with the controller 108 andwith the proportional valve 112 to adjust the flow of the carrier gas tothe delivery device 102. By adjusting proportional valve 112, the amountof the precursor vapor in the carrier gas in the stream 206 can beadjusted to be substantially constant. The flow rate of the carrier gaswith the entrained precursor vapor in the third stream 206 depends onthe demand of the mass flow controller 208 and is controlled by thesecond controller 110 and the second proportional valve 114.

For example, when the concentration of precursor vapor drops relative tothe carrier gas in the third stream 206, an electrical communicationfrom the physical-chemical sensor 104 to the controller 108 and thefirst proportional valve 112 increases the flow of the carrier gas tothe delivery device 102 via the first stream 202 that includes the valve116 and the inlet valve 120. Concurrently the bypass flow 204 is reducedby the same amount. This increases the amount of the precursor vapor inthe carrier gas in the third (combined) stream 206. The increase in theamount of the precursor vapor in the stream 203 when combined with thereduced mass flow rate in the second stream 204 produces a third stream206 that has a concentration of precursor vapor that is substantiallyconstant when compared with the amount of precursor vapor prior to thedecrease that brought about the adjustment in the flow rate of the firststream 202.

In another embodiment, when the concentration of precursor vaporincreases in the third stream 206, an electrical communication from thephysical-chemical sensor 104 to the controller 108 and the proportionalvalve 112 decreases the carrier gas flow though the delivery device 102via the first stream 202. This leads to an increase of the carrier gasflow in the second stream 204. The increase in the carrier gas flow inthe second stream 204 when combined with the decreased carrier gas flowin the first stream 202 produces a third stream 206 that has aconcentration of precursor vapor that is substantially constant whencompared with the amount of precursor vapor prior to the decrease thatbrought about the adjustment in the flow rate of the second stream 204.

The readings from the physical-chemical sensor 104 and the pressuresensor 106 are thus used to adjust or to maintain a narrowly controlledprecursor vapor concentration and the flow rate of the precursor vaporto the reactor 200.

As noted above, the delivery system 100 described herein is advantageousin that it uses the first stream 202 (i.e., the source flow) and thesecond stream 204 (i.e., the bypass flow) to lower the dew point of theprecursor vapor in the carrier gas to below the ambient temperature ormore preferably the temperature of the connecting tubing and hardwarecarrying the third flow 206.

FIG. 2 depicts another embodiment of the delivery system 100 where thecarrier gas is split into the first stream 202 (that flows through theliquid precursor compound and emerges as stream 203) and the secondstream 204 (that bypasses the liquid precursor compound) and isrecombined to form the third stream 206, where the dew point is belowthe ambient temperature. The flow direction of the first stream 202, theflow direction of the second stream 204 and the flow direction of thethird stream 206 are unidirectional and are not opposed to each other.As noted above, there are no opposing flows in the delivery system,except when a mixing chamber is used. This is because using opposingflows in the delivery system do not produce the desired mixing betweenthe carrier gas and the precursor vapor, which results in the deliveryan uneven distribution of the precursor vapor to the plurality ofreactors.

The delivery system 100 in the FIG. 2 is almost similar to the deliverysystem of the FIG. 1 with the exception of the position of the secondproportional valve 114 and a needle valve 119. In this depiction, asingle proportional valve 114 driven by controller 110 in communicationwith the pressure sensor 106 is used to control the pressure in theentire delivery system 100. The delivery system 100 of the FIG. 2comprises at least two closed loops for adjusting the pressure and theprecursor vapor concentration in the carrier gas.

As may be seen in FIG. 2, the first proportional valve 112 liesdownstream of the second proportional valve 114 and may optionally beslaved to the second proportional valve 114. A needle valve 119 liesdownstream of the shutoff valve 118. The needle valve 119 facilitates anadjustable drop in pressure that can be used to adjust the flow of thecarrier gas through the first proportional valve 112 and the deliverydevice 102.

FIG. 3 depicts yet another embodiment of the delivery system 100 thatcomprises a plurality of pressure regulators in communication with thedelivery device 102. The pressure regulators function to promote a dropin the pressure of the incoming carrier gas to a pressure level that isused for the mass flow controller 208.

In this embodiment, the delivery system 100 comprises a first pressureregulator 96 and a second pressure regulator 98 that lies downstream ofthe first pressure regulator 96. The first pressure regulator 96facilitates a drop in pressure of the incoming carrier gas from a firstpressure Pi to a second pressure P2, while the second pressure regulator98 facilitates a further drop in the pressure from the second pressureP2 to a third pressure P3. The first pressure Pi is greater than orequal to the second pressure P2, which is greater than or equal to thethird pressure P3.

In one embodiment, the second pressure P₂ is 50% to 90% of the firstpressure P₁, preferably 55% to 65% of the first pressure P₁. In anexemplary embodiment, the second pressure P₂ is 70% to 85% of the firstpressure P₁. The third pressure P₃ is 40% to 48% of the first pressureP₁, preferably 43% to 47% of the first pressure P₁.

The first pressure P₁ is 1,900 to 2,100 torr (250 to 280 kPa),preferably 1,950 torr to 2,050 torr (260 to 275 kPa). The secondpressure P₂ is 950 torr to 1,400 torr (125 to 190 kPa), preferably 1,000torr to 1,300 torr (130 to 175 kPa). The third pressure P₃ is 500 to 950torr (65 to 125 kPa), preferably 850 torr to 925 torr (110 to 120 kPa).The delivery device 102 can thus operate in conjunction with a reactor200 whose inlet pressure is 500 to 2,000 torr (65 to 260 kPa),preferably 700 to 1800 torr (90 to 240 kPa), and more preferably is 900torr (120 kPa). The reactor 200 by operating in the range between 50 and760 torr (6 to 101 kPa) thus extracts via the mass flow controller 208from the delivery device 100 the precise precursor vapor that is usedfor the chemical reaction that occurs in the reactor.

Disposed downstream of the first pressure regulator 96 are the firstproportional valve 112, a shutoff valve 116, the inlet valve 120, thedelivery device 102, the outlet valve 122 and the physical-chemicalsensor 104. The first proportional valve 112 is disposed downstream ofthe first pressure regulator 96 and upstream of the second pressureregulator 98.

The first pressure regulator 96 is in fluid communication with the firstproportional valve 112, a shutoff valve 116, the inlet valve 120, thedelivery device 102, the outlet valve 122 and the physical-chemicalsensor 104. The fluid stream that includes the first pressure regulator96, the first proportional valve 112, a shutoff valve 116, the inletvalve 120, the delivery device 102, the outlet valve 122 and thephysical-chemical sensor 104 lie is termed the first stream 202. Thefirst stream 202 directs the carrier gas to the inlet port of thedelivery device 102.

The physical-chemical sensor 104 is in communication with the firstproportional valve 112. In one embodiment, the physical-chemical sensor104 is in electrical communication with the first proportional valve112. The proportional valve 112, a shutoff valve 116, the inlet valve120, the delivery device 102, the outlet valve 122 and thephysical-chemical sensor 104 are in a closed loop.

The second pressure regulator 98 is disposed upstream of shutoff valve118 and the mixing chamber 107. The fluid stream that includes thesecond regulator 98 and the second valve 118 is termed the second stream204.

The stream 203 emanating from the delivery device contacts the secondstream 204 to form the third stream 206. In one embodiment, the stream203 contacts the second stream 204 downstream of the outlet valve 122 ofthe delivery device 102. The physical-chemical sensor 104 is disposeddownstream of the outlet valve 122. Output signals from thephysical-chemical sensor 104 are directed to the first proportionalvalve 112 through the first controller 108.

In one manner of operating the delivery system 100 of the FIG. 3, thereactor 200 draws a mixture of the precursor vapor and the carrier gasfrom the delivery device 102. The physical-chemical sensor 104 measuresthe precursor vapor concentration and/or the flow rate (or pressure) inthe third stream 206. If the precursor vapor concentration and/or theflow rate in the third stream 206 lie outside desired limits, the sensor104 communicates with the first proportional valve 112 through the firstcontroller 108. The first controller 108 increases or reduces thevoltage to the first proportional valve 112. By closing or opening theproportional valve 112, the flow rate (or the pressure) of the carriergas or the concentration of the precursor vapors in the carrier gas willbe adjusted to a desired value.

In one method of manufacturing the delivery system 100, the proportionalvalves 112 and/or 114 are disposed upstream of the delivery device 102.Shutoff valves 116 and/or 118 are disposed downstream of theproportional valves 112 and/or 114 respectively and upstream of thedelivery device 102. The delivery device 102 is disposed in a heatedenclosure 103. The inlet valve 120 and the outlet valve 122 are disposedat the inlet and the outlet respectively of the delivery device 102. Thephysical-chemical sensor 104 and the pressure sensor 106 are disposeddownstream of the delivery device 102 and form closed loops with theproportional valves 112 and/or 114 respectively. The delivery system 100is in fluid communication with the reactor 200 via a mass flowcontroller 208. The mass flow controller 208 is disposed upstream of thereactor 200.

The delivery system 100 is advantageous in that it can deliver aconstant stream of precursor vapor at a larger flow rate than othercomparative devices. The method does not involve any opposing flows. Theflow throughout the delivery system 100 involves flow in a singledirection. This produces better mixing between the carrier gas and theliquid precursor vapor. Systems that have opposing flows suffer from theproblems that occur when one of the flows increases in pressure over theother flow. This produces a non-uniform supply of the precursor vapor tothe reactors.

The system 100 also permits the delivery of a uniform and highly preciseconcentration of the liquid precursor compound to the reactor 200. Thisfeature distinguishes the system 100 over other comparative deliverysystems that attempt to supply a uniform concentration of the liquidprecursor compound to the reactor. The delivery of a constant number ofmoles per unit time generally can be obtained by generating a constantnumber of moles per unit volume, especially when the system has opposingflows of carrier gas. Fluctuations of precursor concentration often giverise to fluctuations of the precursor per unit time that is delivered tothe reactor, which leads to the production of non-conforming product.

The disclosed system 100 also permits a uniform mass flow of theprecursor to the reactor over a large period of time of 10 minutes toseveral months. In one embodiment, the delivery system 100 can deliverthe precursor vapor at rates greater than or equal to 1,500 micromolesper minute, preferably greater than or equal to 1,750 micromoles perminute and more preferably greater than or equal to 2,000 micromoles perminute at a temperature of greater than or equal to 15° C. and apressure of greater than or equal to 900 torr (120 kPa), whilemaintaining carrier gas flow rates of greater than or equal to 1standard liters per minute (slm), preferably greater than or equal to 2standard liters per minute, and more preferably greater than or equal to3 standard liters per minute to the reactor 200.

The following example was conducted to demonstrate that the discloseddelivery device delivers a steady concentration of liquid precursorcompound to the reactor when compared with a comparative deliverydevice. FIG. 6 is a depiction of a comparative prior art delivery device400 that comprises a 1 standard liter per minute mass flow controller402, a constant temperature bath 404, a thermometer 406 immerseddirectly into the liquid precursor compound and a binary gasconcentration sensor 408. The carrier gas is nitrogen. Carrier gas flow,the liquid precursor compound temperature and vapor concentration wererecorded every second. The liquid precursor compound wastrimethylgallium.

FIGS. 7A and 7B show the response of the liquid precursor compoundtemperature and the liquid precursor compound vapor concentration tostep changes in the flow for a 4.6 kilogram (kg) cylinder with an aspectratio of close to 1. These step changes are common when the source isturned on for epitaxy or when a reactor is added or dropped from thesupply in cluster tools. The change in flow will change thetrimethylgallium flux to the other reactors that are online. The bathtemperature for the experiments was 5° C. The total pressure was 101 kPa(760 ton).

FIG. 7A shows the response of the cylinder at a fill level of 40% (1.8kg). Although the bath temperature was 5.0° C., the temperature of thetrimethylgallium was 5.7° C. at no flow. In the setup shown in the FIG.6, the top of the cylinder was not immersed into the bath and the heatfrom the surrounding air heated the trimethylgallium. After switchingthe flow to 1 standard liter per minute (slm) it took thetrimethylgallium 85 minutes or 25 grams to reach steady state beforesteady state was reached and the carrier gas along with the entrainedvapor could be fed to the reactor to being epitaxial growth. At 1 slmthe temperature difference is 0.7° C. which means that only 0.971× ofthe intended trimethylgallium a flux is actually reaching the substrate.

FIG. 7B shows the same cylinder at a fill level of 20% (820 grams).After switching the flow to 1 slm, the time to steady state is 95minutes, which is no significant change from a cylinder filled to the40% fill point. Since the heat transfer area is reduced from theprevious experiment (i.e., the 40% fill level) the temperaturedifference has increased to 1.4° C. The trimethylgallium flux is 0.94×of the intended flux.

The incorporation of sophisticated engineering controls for everycylinder to correct for the variation in flux would add costs to theinfrastructure that are prohibitively high. Therefore, the industryemploys correction charts to address shifts in flux over the life of thecylinder. This means that every tool has to be individually tuned forevery run. Uncertainty in tuning lowers epitaxy yields. It should benoted that for cylinders larger than 4 kg the time to reach steady stateis longer and the shifts during the life of the cylinder are morepronounced. The longer the time to reach steady-state, the higher theamount of trimethylgallium that is sent wasted (i.e., vented to outsidethe system) before epitaxial growth can be initiated.

From FIGS. 7A and 7B it may be seen that every time the rate of flow ofthe carrier gas is changed, there is a significant change in thetemperature of the liquid precursor compound. This change in temperatureis accompanied by a significant change in the concentration oftrimethylgallium in the carrier gas. Not only is there a change inconcentration of the liquid precursor compound in the vapor stream, butit takes a considerable amount of time for the change in concentrationto level off at a certain concentration (steady state), that may befound with the help of charts and corrected for when running theprocess. This change in concentration as well as the accompanyinginertia (the amount of time taken to return to the steady state) isundesirable and can be overcome by using the disclosed delivery device.

The delivery device detailed in this disclosure was also tested and hasthe same configuration as that depicted in the FIG. 3. The concentrationwas maintained in the carrier gas flow range from 0 to 2 slm. The totalpressure was 101 kPa (760 ton). The trimethylgallium cylinder was in achemical hood with no provision to regulate the trimethylgalliumtemperature. The liquid precursor compound for this example was alsotrimethylgallium. The knowledge of the exact temperature of thetrimethylgallium is not necessary for the new delivery system to work.The results are detailed in the FIG. 8. The FIG. 8 contains data for theconventional delivery device as well as for the disclosed deliverydevice. From FIG. 8 it can be seen that there is a significant change intrimethylgallium concentration for the conventional device when a changein the amount of the carrier gas supplied to the delivery device takesplace. However, for the disclosed delivery device of FIG. 3, theconcentration immediately returns to its set concentration following achange in the amount of carrier gas supplied to the delivery device.

In summary, the concentration of the liquid precursor compound vaporsper unit volume fluctuates in an amount of less than or equal to 1 wt %,preferably in an amount of less than or equal to 0.5 wt %, and morepreferably in an amount of less than or equal to 0.25% over a period oftime of 10 minutes to several months from a selected value for adelivery device that carries more than 0.5 kilograms of the liquidprecursor compound, preferably more than 4 kilograms of the liquidprecursor compound, and more preferably more than 10 kilograms of theliquid precursor compound. In one embodiment, the delivery device usesan amount of energy of greater than or equal to about 1 watt, preferablygreater than or equal to about 3 watts, and more preferably greater thanor equal to about 5 watts in order to vaporize the liquid precursor anddeliver it to the reactor. The greatly reduced volume fluctuations inthe delivery of the precursor compound translate into greatly reducedfluctuations over large amounts of time. The chemical vapor deposition(CVD) process relies on a uniform and known precursor compound per unittime feed. The present invention increases the precision of this feedfrom 10 wt % obtained with conventional devices to 0.2 wt % over largeperiods of time.

What is claimed is:
 1. A method comprising: transporting a first streamof a carrier gas to a delivery device, the delivery device containing aliquid precursor compound, the first stream of carrier gas being at atemperature greater than or equal to 15° C., wherein the liquidprecursor compound is in a liquid state in the delivery device;transporting a second stream of the carrier gas to a point downstream ofthe delivery device, wherein a flow direction of the first stream and aflow direction of the second stream are not opposed to each other;combining the first stream after emanating from the delivery device andthe second stream to form a third stream; wherein a dew point of a vaporof the liquid precursor compound in the third stream is lower than anambient temperature; analyzing chemical contents of the third streamdisposing a physical-chemical sensor downstream of the delivery device;providing the physical-chemical sensor is in communication with aproportional valve; providing a first controller in operativecommunication with the physical-chemical sensor and with theproportional valve; providing at least one second controller inoperative communication with the physical-chemical sensor and with atleast one of a plurality of reactors; and transmitting a signal from thephysical-chemical sensor that is disposed in the third stream to atleast one of a first regulator and a second regulator.
 2. The method ofclaim 1, wherein the first regulator is operative to control a flow rateof a carrier gas in the first stream, and wherein the second regulatoris operative to control a flow rate of a carrier gas in the secondstream.
 3. The method of claim 1, wherein the proportional valve isdisposed downstream of the first regulator, and wherein the secondregulator is disposed downstream of the first regulator.
 4. The methodof claim 1, wherein the signal from the physical-chemical sensor isreceived by the first regulator and the first regulator facilitates afirst drop in pressure of the first stream from a first pressure to asecond pressure.
 5. The method of claim 4, wherein the second regulatorreceives at least one of the signal or a second signal and the secondregulator facilitates a second drop in pressure of the first stream fromthe second pressure to a third pressure.
 6. The method of claim 1,wherein the at least one of a plurality of reactors extracts the vaporof the liquid precursor compound from the delivery device using the atleast one second controller.
 7. A delivery system for a liquid precursorcompound comprising: a first regulator; a second regulator; aproportional valve disposed downstream of the first regulator and beingin fluid communication with the first regulator; a delivery devicedisposed downstream of a first shutoff valve and having an inlet valveand an outlet valve; a physical-chemical sensor disposed downstream ofthe delivery device and being operative to analyze chemical contents ofa fluid stream emanating from the delivery device, the physical-chemicalsensor being in communication with the proportional valve; a firstcontroller being in operative communication with the proportional valveand the physical-chemical sensor; at least one second controller beingin operative communication with the physical-chemical sensor and withthe proportional valve; at least one reactor being in operativecommunication with the at least one second controller to extract theprecursor vapor from the delivery device; and wherein the deliverysystem is operative to deliver a substantially constant number of molesof a liquid precursor compound vapor per unit volume of a carrier gas toa reactor that is in communication with the delivery system, wherein theliquid precursor compound is in a liquid state in the delivery device,wherein the proportional valve is in electrical communication with thefirst controller, and wherein the proportional valve is operative tocontrol the flow of the carrier gas based on an applied voltage.
 8. Thedelivery system of claim 7, wherein the proportional valve, the firstshutoff valve, the inlet valve, the delivery device, the outlet valve,and the physical-chemical sensor lie in a closed loop.
 9. The deliverysystem of claim 7, wherein the first regulator is disposed upstream ofthe second regulator.
 10. The delivery system of claim 7, wherein thedelivery system is operative to deliver vapor of the liquid precursorcompound at a rate greater than or equal to 1,500 micromoles per minuteat a carrier gas flow rate of greater than or equal to 1 standard litersper minute at a temperature of greater than or equal to 15° C. and apressure of greater than or equal to 120 kilopascals.
 11. The deliverysystem of claim 7, wherein the delivery system is operative to maintaina precise vapor concentration within ±0.5 wt % from a set point anddeliver the precursor vapor to the plurality of reactors.
 12. Thedelivery system of claim 7, wherein all flows in the delivery system areunidirectional and none of the flows are opposed to each other.
 13. Thedelivery system of claim 7, wherein the first pressure regulatorfacilitates a drop in pressure of the incoming carrier gas from a firstpressure P₁ to a second pressure P₂.
 14. The delivery system of claim13, wherein the second pressure regulator facilitates a drop in pressurefrom the second pressure P₂ to a third pressure P₃.
 15. The deliverysystem of claim 14, wherein the first pressure P₁ is greater than orequal to the second pressure P₂, and wherein the second pressure P₂ isgreater than or equal to the third pressure P₃.
 16. The delivery systemof claim 7, wherein the delivery system is in fluid communication withthe at least one reactor via the at least one second controller.
 17. Thedelivery system of claim 7, wherein the at least one second controlleris one controller and the at least one reactor is a plurality ofreactors.
 18. The delivery system of claim 7, further comprising: afirst shutoff valve disposed downstream of the proportional valve; and asecond shutoff valve disposed downstream of the second pressureregulator.
 19. The delivery system of claim 7, further comprising: amixing chamber disposed downstream of the delivery device and the secondshutoff valve.
 20. The delivery system of claim 6, wherein the at leastone second controller is a mass flow controller.